Background sound pressure fluctuations (5 dB) from overhead ventilation systems increase subjective fatigue of university students during three-hour lectures

During each of four successive sessions (once per week), 21 university stud ents attended 3-hr. lectures. During alternative weeks the fans of the room 's ventilation system were either on or off. When operating, they generated an average sound pressure that varied continuously between 60 and 65 dB. T he dominant frequency of this 5-dB amplitude modulation of sound pressure w as within the electroencephalographic range (5 Hz to 25 Hz). At the end of each hour of the lecture for each session each student estimated on 7-point summated rating scales fatigue (none to maximum) and concentration (poor t o excellent). As a group, the students report ed more fatigue during lectur es when the fans were operating relative to lectures when the fans were not operating. This environmental effect explained about 30% of the variance i n fatigue ratings and may be sufficient to affect adversely the attention o f students within these settings.